CH 12 Electrophysiology of a neuron

Question 1

K+ Concentration in ICF/ECF

Answer 1

150mM
4mM

Question 2

Na+ Concentration in ICF/ECF of neuron

Answer 2

20mM
145mM

Question 3

Ca^2+ Concentration in ICF/ECF of neuron

Answer 3

.0001 mM
2.5mM

Question 4

Cl- Concentration in ICS/ECF of neuron

Answer 4

7mM
150mM

Question 5

How do ions move across the membrane?

Answer 5

In ionic channels through facilitated diffusion; passive transport that moves from high concentration to low concentration

Question 6

What does it mean for a neuron to be polarized?

Answer 6

It has a charge

Question 7

Resting membrane potential of a neuron

Answer 7

-70mV

Question 8

Causes of resting membrane potential

Answer 8

1. Ionic diffusion
2. Selectively permeable membrane
3. Electrical attraction of ions

Question 9

Which ion has the most influence on resting membrane potential? Second most?

Answer 9

Potassium (K+)
Sodium (Na+)

Question 10

Is membrane more permeable to potassium or sodium?

Answer 10

Potassium, which makes it more negative resting membrane potential because positive ions leaving the cell

Question 11

Na+/K+ ATPase Pump

Answer 11

3 Na+ out, 2 K+ in

Active transport pump that uses ATP to maintain resting membrane potential;  replenishes leakage of sodium and potassium

Question 12

 Ligand

Answer 12

A chemical that binds to a receptor

Question 13

Local potential: Graded

Answer 13

1. Graded (Magnitude based on strength of stimulus)

Question 14

Local potential: local

Answer 14

Membrane change the only happens in region to which stimulus is occurring

Question 15

Local potential: reversible

Answer 15

When you stop releasing ligands, return to resting membrane potential

Question 16

Local potential: excitatory or inhibitory

Answer 16

Inhibitory= Hyperpolarizing; more neg so Takes extra stimulus to reach threshold

Excitatory= Depolarization; bringing closer to zero; if stimulus strong enough, will reach threshold and fire action potential

Question 17

Action potential

Answer 17

If threshold is reached, opening of voltage gated ionic channels move depolarization down the axon. All or none

Question 18

Voltage gated Na+ channels

Answer 18

Open: At -55mV (threshold), channel opens and Na+ rushes into cell causing depolarization.

Inactive gate: at +35mV Dongle on bottom of gate Blocks it.…lag period, then swings off and top gate closes

Question 19

Voltage gated K+ Channels

Answer 19

At +35 mV VG K+ opens and K+ rushes out causing rapid hyperpolarization… the goes back to normal

Question 20

Steps to an action potential

Answer 20

1. Local potential depolarizes membrane
2. Threshold (-55mV) reached and VG Na+ channels open
3. Depolarization; Na+ rushes in cell
4. Overshoot; at +35 mV VG Na+ channels close and VG K+ channels open
5. Repolarization; K+ rushes out of cell
6. Hyperpolarization; because of slow closing of VG K+ channels
7. Return to RMP ; Via Na+/K+ ATPase pump

Question 21

Absolute refractory period

Answer 21

Can’t fire another action potential; Inactivated Voltage gate sodium channel (the dongle)

Question 22

Relative refractory period

Answer 22

During hyperpolarization can fire another action potential if greater stimuli causes threshold to be reached

Question 23

Nerve signal

Answer 23

Action potential moving down axon

Question 24

Unmyelinated conduction

Answer 24

Continuous conduction
Speed: slower 2 M/s

Question 25

Myelinated conduction

Answer 25

Saltatory conduction; jumps

Speed: Faster, 120M/s